1. Field of Invention
The present invention relates to improvements in the manufacture and assembly of bolted-on structures, such as automotive exhaust manifold gaskets of internal combustion engines. More particularly, the invention relates to improved gaskets having bolt apertures including unique spring structures for retaining bolt members in place on such gaskets prior to their installation in engines.
2. Description of the Prior Art
Those skilled in the art will appreciate the difficulty of assembling an exhaust manifold gasket between a cylinder head exhaust port of an internal combustion engine and an exhaust manifold flange normally secured thereto via bolts. Typically, the exhaust manifold gasket is placed on a radially inwardly directed flank or side of the engine. As a result, the manifold gasket must be applied to the engine at occasionally awkward angles, and thus can be quite difficult to assemble to the engine. In addition, the art of maintaining the gasket in place on the engine while attaching and securing the exhaust manifold thereto can be even more difficult.
One method has involved attaching and holding the gasket in place on the manifold prior to installation of the manifold. This approach has enjoyed limited success because typical methods of attachment of gaskets to the manifolds for shipment have included such items as clips in varied assortments and arrangements. Such clips often tend to break or become loose, and the gaskets often become detached during shipment.
Another method has involved securing the gasket to the manifold via bolts already at least partially secured in place to the manifold. This method has purported to reduce the number of components requiring handling, and thus has promised greater efficiency of assembly. However, the method has instead been relatively labor-intensive in that the bolts have had to be partially threaded within threaded apertures of the manifold. This effort has required manual rotary manipulation of each bolt for its proper securement. A better method would be the employment of a simple push-style insertion of each bolt into a manifold aperture. The resultant reduction in the labor burden would provide an attractive solution to noted issues of shipping, handling, and installation.
The present invention is a bolt retainer mechanism incorporating at least two tabs formed directly in a first bolt aperture of one layer of a multiple-layered steel (MLS) gasket. Each tab is formed to define an inverted U-shaped tang that extends adjacent to, and is in symmetrical registration with, while axially spaced from, an associated mated second aperture formed in the bottom layer of at least a two-layer gasket. Collectively, the plurality of such tangs define a circumscribed diameter slightly smaller than the diameter of the mated second aperture in order to ensure retention of a bolt through both aligned apertures of first and second gasket layers, particularly during pre-assembly shipment.
In one described embodiment, the tangs at each first aperture are formed of a spring metal and are adapted to provide radially inwardly directed forces against the threaded shanks of associated bolts for retention of the bolts under conditions of handling and vibration. Also, the bolt-contacting portion of each inverted U-shaped tab has an axial length greater than the two-layer axial thickness of the mated apertures. Thus, the depth of engagement afforded to the shank any given bolt by the inverse legs of the U-shaped tab is particularly effective to enhance retention of the bolt within the apertures.